Engine components in the hot gas flow of modern combustion turbine engines are required to operate at ever-increasing temperatures as engine efficiency requirements continue to advance. Ceramics typically have higher heat tolerance and lower thermal conductivities than metals. For this reason, ceramics have been used both as structural materials in place of metallic materials and as coatings for both metal and ceramic structures. Ceramic matrix composite (CMC) structures with ceramic thermal insulation outer coatings have been developed to provide components with the high temperature stability of ceramics without the brittleness of monolithic ceramics. An especially effective type of ceramic thermal barrier insulation coating is described in commonly owned U.S. Pat. No. 6,197,424 which has come to be known as friable graded insulation (FGI). The coating includes a plurality of hollow oxide shapes, a binder, and at least one oxide filler powder. The oxide shapes, which may be spheres, are situated in the phosphate binder and the filler powders such that each sphere is in contact with at least one other sphere, and the arrangement of spheres is such that the composition is dimensionally and chemically stable at temperatures of approximately 1600° C. A challenge facing optimization of insulated CMC structures is the effectiveness of joining of the CMC material and the insulation layer, given that the insulation layer is typically cast onto a partially processed substrate representing a different state of process shrinkage.